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K2 filter alignment problem

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K2 filter alignment problem

I have aligned my K2 crystal filters with Spectogram many times, but
this time I've run into a problem that I can't figure out.

Using Don's [and the manual's] instructions, I can align F1,F2,F3 in
decreasing bandwidths. All works as per expectations. On F4, the
alignment goes "ok," [as per Spectogram] but when I use it with
on-the-air signals, the signal "disappears" and shows up about 900 cps
lower and in "reverse" orientation [BFO on opposite side]. When the
signal disappears, I can change filters [F1/F2/F3] and it's right there
where it should be with the bandwidth getting narrower as expected. But,
switching to F4, it's gone. I have tried changing the BFO frequency
throughout its whole range when in F4, thinking that I've aligned it on
the "wrong" side. No luck. I'm stumped. Any and all suggestions welcomed.

...robert
--
Robert G Strickland, PhD ABPH - KE2WY
[hidden email]
Syracuse, New York, USA
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Don Wilhelm

Re: K2 filter alignment problem

Richard,

Try widening the FL4 filter out to 0.2 instead of 0.1. With the more
narrow setting there is often more attenuation with little actual
reduction in width.

When aligning the BFOs, pay attention to the DAC values (and/or
frequencies). The ones for CW must be less than the filter center and
those for CWrev must be greater than the filter center. Normally the CW
FL4 will have a BFO frequency near 4913.12 and for CWrev a frequency
near 4914.3 kHz.

Make certain when aligning the filters with Spectrogram you use a source
of wideband noise. If you are using 'antenna noise', be certain there
are no signals nearby.

73,
Don W3FPR

On 4/10/2019 9:28 PM, Robert G Strickland via Elecraft wrote:

> I have aligned my K2 crystal filters with Spectogram many times, but
> this time I've run into a problem that I can't figure out.
>
> Using Don's [and the manual's] instructions, I can align F1,F2,F3 in
> decreasing bandwidths. All works as per expectations. On F4, the
> alignment goes "ok," [as per Spectogram] but when I use it with
> on-the-air signals, the signal "disappears" and shows up about 900 cps
> lower and in "reverse" orientation [BFO on opposite side]. When the
> signal disappears, I can change filters [F1/F2/F3] and it's right there
> where it should be with the bandwidth getting narrower as expected. But,
> switching to F4, it's gone. I have tried changing the BFO frequency
> throughout its whole range when in F4, thinking that I've aligned it on
> the "wrong" side. No luck. I'm stumped. Any and all suggestions welcomed.

______________________________________________________________
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Elecraft mailing list

Re: K2 filter alignment problem

Don...

Bingo! The F4 filter setting was too narrow, as you advised. Also, the
BFO was somewhere off from where it belonged. Once I got those two item
adjusted everything worked as per specs. I was impressed that the BFO
values that you quoted were more or less right on. Seems like you have
some experience with the K2 :-). Thanks much for your time and
attention, as always. Have a good day.

...robert

On 4/11/2019 14:00, Don Wilhelm wrote:

> Richard,
>
> Try widening the FL4 filter out to 0.2 instead of 0.1. With the more
> narrow setting there is often more attenuation with little actual
> reduction in width.
>
> When aligning the BFOs, pay attention to the DAC values (and/or
> frequencies). The ones for CW must be less than the filter center and
> those for CWrev must be greater than the filter center. Normally the CW
> FL4 will have a BFO frequency near 4913.12 and for CWrev a frequency
> near 4914.3 kHz.
>
> Make certain when aligning the filters with Spectrogram you use a source
> of wideband noise. If you are using 'antenna noise', be certain there
> are no signals nearby.
>
> 73,
> Don W3FPR
>
> On 4/10/2019 9:28 PM, Robert G Strickland via Elecraft wrote:
>> I have aligned my K2 crystal filters with Spectogram many times, but
>> this time I've run into a problem that I can't figure out.
>>
>> Using Don's [and the manual's] instructions, I can align F1,F2,F3 in
>> decreasing bandwidths. All works as per expectations. On F4, the
>> alignment goes "ok," [as per Spectogram] but when I use it with
>> on-the-air signals, the signal "disappears" and shows up about 900 cps
>> lower and in "reverse" orientation [BFO on opposite side]. When the
>> signal disappears, I can change filters [F1/F2/F3] and it's right
>> there where it should be with the bandwidth getting narrower as
>> expected. But, switching to F4, it's gone. I have tried changing the
>> BFO frequency throughout its whole range when in F4, thinking that
>> I've aligned it on the "wrong" side. No luck. I'm stumped. Any and all
>> suggestions welcomed.
>

--
Robert G Strickland, PhD ABPH - KE2WY
[hidden email]
Syracuse, New York, USA
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
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Don Wilhelm

Re: K2 filter alignment problem

Robert,

Yes, I have 20 years experience with the K2. I have seen many "strange"
problems on my years repairing them, some are user induced.

73,
Don W3FPR

On 4/11/2019 7:46 PM, Robert G Strickland wrote:

> Don...
>
> Bingo! The F4 filter setting was too narrow, as you advised. Also, the
> BFO was somewhere off from where it belonged. Once I got those two
> item adjusted everything worked as per specs. I was impressed that the
> BFO values that you quoted were more or less right on. Seems like you
> have some experience with the K2 :-). Thanks much for your time and
> attention, as always. Have a good day.
>
> ...robert
>